In one weekend in 1967, two occurrences at opposite ends of the world began the process whereby Americans convinced themselves that the Vietnam War was not worth fighting.
One of these was the ambush of an American battalion by the Vietcong, resulting in 61 casualties. The other was at the University of Wisconsin at Madison, where state police ejected students who were campaigning against the presence presence on campus of recruiting agents for napalm manufacturers Dow Chemical.
This brilliant film works so well because its focus is so narrow. We see survivors of the ambushed battalion and we see the women who lost their husbands and who still recall, so many years later, their grief.
We are also able to understand how, throughout universities in America, students became, (in the word of the time), 'radicalised' through their opposition to the war.
It's interesting, of course, to compare those events with the American scene now: with the war in Iraq, opposition has likely been milder because the American army no longer relies on the draft.
